CA2155559A1 - Process for the production of dinitrotoluene - Google Patents
Process for the production of dinitrotolueneInfo
- Publication number
- CA2155559A1 CA2155559A1 CA002155559A CA2155559A CA2155559A1 CA 2155559 A1 CA2155559 A1 CA 2155559A1 CA 002155559 A CA002155559 A CA 002155559A CA 2155559 A CA2155559 A CA 2155559A CA 2155559 A1 CA2155559 A1 CA 2155559A1
- Authority
- CA
- Canada
- Prior art keywords
- acid
- weight
- phase
- nitric acid
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 44
- DYSXLQBUUOPLBB-UHFFFAOYSA-N 2,3-dinitrotoluene Chemical compound CC1=CC=CC([N+]([O-])=O)=C1[N+]([O-])=O DYSXLQBUUOPLBB-UHFFFAOYSA-N 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000002253 acid Substances 0.000 claims abstract description 85
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims abstract description 42
- 230000000802 nitrating effect Effects 0.000 claims abstract description 40
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 36
- 239000012071 phase Substances 0.000 claims abstract description 29
- ZPTVNYMJQHSSEA-UHFFFAOYSA-N 4-nitrotoluene Chemical compound CC1=CC=C([N+]([O-])=O)C=C1 ZPTVNYMJQHSSEA-UHFFFAOYSA-N 0.000 claims abstract description 26
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000012074 organic phase Substances 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 229910010272 inorganic material Inorganic materials 0.000 claims description 10
- 239000011147 inorganic material Substances 0.000 claims description 10
- 239000011541 reaction mixture Substances 0.000 claims description 7
- 238000001704 evaporation Methods 0.000 claims description 5
- 230000008020 evaporation Effects 0.000 claims description 5
- 239000011368 organic material Substances 0.000 claims description 5
- VLZLOWPYUQHHCG-UHFFFAOYSA-N nitromethylbenzene Chemical class [O-][N+](=O)CC1=CC=CC=C1 VLZLOWPYUQHHCG-UHFFFAOYSA-N 0.000 claims description 4
- 238000004064 recycling Methods 0.000 claims description 3
- 238000010924 continuous production Methods 0.000 claims description 2
- VMMLSJNPNVTYMN-UHFFFAOYSA-N dinitromethylbenzene Chemical class [O-][N+](=O)C([N+]([O-])=O)C1=CC=CC=C1 VMMLSJNPNVTYMN-UHFFFAOYSA-N 0.000 claims description 2
- 238000006396 nitration reaction Methods 0.000 abstract description 20
- 150000007513 acids Chemical class 0.000 abstract description 5
- 239000007795 chemical reaction product Substances 0.000 abstract description 2
- 239000011369 resultant mixture Substances 0.000 abstract 1
- 239000002699 waste material Substances 0.000 description 22
- 238000000576 coating method Methods 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 238000005191 phase separation Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
- C07C205/06—Compounds containing nitro groups bound to a carbon skeleton having nitro groups bound to carbon atoms of six-membered aromatic rings
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Dinitrotoluene is produced in a two-stage process from toluene and nitric acid in the presence of sulfuric acid under adiabatic conditions in the presence of nitrating acids made up of specified components. The reaction product of the first phase is separated into an acid phase and an organic phase containing the mononitrotoluene. Some water is removed from the acid phase, nitric acid is added and the resultant mixture is recycled. The organic phase containing mononitrotoluene is further nitrated to produce the dinitrotoluene. This nitration mixture is also separated into an acid phase and an organic phase. The acid phase is treated to remove some water, nitric acid is added and the resultant acid mixture is recycled. Dinitrotoluene is recovered from the organic phase.
This process is advantageous in that dilute nitric acid may be used and the heat of the nitration reaction is utilized.
This process is advantageous in that dilute nitric acid may be used and the heat of the nitration reaction is utilized.
Description
215~S9 Mo4239 LeA 30,601 -A PROCFSS FOR THF PRODUCTION OF DINITROTOI U~NF
BACKGROUND OF THF INVFI~ITION
This invention relates to a two-stage process for the production of dinitrotoluene from toluene and nitric acid in the presence of sulfuric acid.
Dinitrotoluene (DNT) is used to produce tolylene diisocyanate - (TDI). TDI is a starting material used in the production of polyurethane plastics. DNTis generally produced by reacting toluene with nitrating acid. This nitration reaction is carried out in two stages. Mononitro-toluene (MNT) is initially obtained by reacting toluene with a dilute nitrating acid. After removal of the spent sulfuric acid (hereinafter referred to as "waste acid"), the MNT is converted to DNT in a second process step. Both nitrating steps are carried out under isothermal conditions, i.e. with cooling to maintain a low temperature.
Two waste acids accumulate in the process and, after regeneration with nitric acid, may be returned to the process. The waste acid from the second stage can be directly recycled. The waste acid from the second stage may still have a concentration such that, after regeneration with nitric acid, it may be used without being concentrated beforehand. Accordingly, only the waste acid from the first stage has to be concentrated before being re-used. This is normally done by the Pauling process (Bedenbrenner, von Plessen, Vollmuller, Dechema-Monogr. 86 (1980), 197) although the vacuum process is also increasingly being used (\Ninnacker, Kuchler, Chem. Technol, Vol. 2, Anorg. Technol. I, 4th Edition, 1982, pages 70 to 72). In both of these acid concentration processes, energy must be introduced to remove the water of reaction.
During its recycling, the concentrated waste acid is replenished with highly concentrated nitric acid. Although nitric acids of low concentration, which are far less expensive, could be used in principle, Mo4239 - 2 -their use does involve the consumption of considerable additional energy because the waste acid has to be concentrated to a higher degree.
For the reasons mentioned above, efforts have long been made to improve the above-described nitration processes.
An improvement in terms of energy consumption may be achieved -by carrying out the mononitration of benzene under adiabatic conditions.
It was also found that it is possible to use more dilute nitric acids in such a process. The adiabatic process has been used industrially. See, for example, U.S. Patents 3,928,475; 4,021,498; 4,091,042 and 4,453,027;
and EP-A 436,443).
The adiabatic process was also applied to the production of aromatic dinitro compounds (EP-A 597,361). In this case, toluene is reacted with nitrating acid in a single stage to form DNT. By using nitrating acids with a special composition, it is possible to carry out the nitrating process under adiabatic conditions and to keep the heat of reaction in the system. There is no longer any need to cool the process, as in the conventional isothermal process, so that expensive cooling energy is saved. After separation of the phases, the hot waste acid is sprayed in vacuo and the heat of reaction of the process is used to concentrate the waste acid. Because the reaction is carried out under adiabatic conditions, i.e. at a high temperature, the process is able to accommodate the use of dilute nitric acid. Depending on the nitric acid used, there is little or no need for heating in the concentration step.
The disadvantage of this latter process is that both mononitration and dinitration are carried out with the same nitrating acid. Because nitration is intended to be quantitative, the reactivity of the nitrating acid has to be adapted to the dinitration step. Accordingly, the nitrating acid used in this known process is actually too concentrated for the mononitration step, so that mononitration takes place very quickly and, in some cases, with very little selectivity. Another disadvantage of this 21~5~9 Mo4239 - 3 known process is that a more concentrated waste acid than necessary accumulates in the mononitration step. Waste acids of relatively high concentration are much more expensive to concentrate in terms of energy because the heat of solution of water in sulfuric acid increases 5 with increasing sulfuric acid concentration.
Another disadvantage of this known process is that DNT dissolved in the waste acid also distills over in the concentration step. Under the conditions required for condensation of the water, the DNT crystallizes, covers the heat exchanger and thus impedes the transfer of heat.
A possible solution to this problem with respect to heat transfer is to use cyclic heat exchangers. Cyclic heat exchangers are operated alternately and any coatings formed are melted off during the phase in which the heat exchanger is not in operation. Coatings forrned on the heat exchange surfaces result in rapid reduction of cooling capacity.
15 Consequently, the heat exchangers need to be frequently alternated.
The removal of coatings formed from the inoperative condenser by melting requires additional energy.
Use of a mixing or injection condenser has been described as another possible solution to the problem of condensing solids-forrning 20 vapors (R.A. Vauck, H.A. Muller, Grundoperationen chemischer Verfahrenstechnik, 5th Edition, VEB Leipzig (1962), page 447). In the mixing or injection condenser, the vapors are introduced into a jet spray of cold water. DNT is deposited in the form of a fine particulate solid when such an injection condenser is used. In view of the large quantities 25 of water required in these processes, the water is circulated and cooled in the return branch of the circuit. However, pipes and nozzles are subject to blockage by low melting, inorganic components which tend to become tacky.
One elegant solution to this problem is the isotherrnal two-stage 30 nitration process. In this process, MNT from the first nitration stage is 21 S 5 3 ~ 9 Mo-4239 4 injected into the vapors of the second concentration stage. The MNT
introduced reduces the melting point of the DNT isomer mixture and the condensed mixture remains liquid (DE-A 3,409,719).
SUMMARY OF THF INVFNTION
It is an object of the present invention to provide a process for the production of dinitrotoluene in which dilute nitric acid may be used.
- It is also an object of the present invention to provide a process for the production of dinitrotoluene which utilizes the heat of reaction.
It is a further object of the present invention to provide a process for the production of dinitrotoluene in which problems due to condensation of the vapors in the waste acid concentration step are avoided.
These and other objects which will be apparent to those skilled in the art are accomplished by nitrating toluene with a nitrating acid satisfying specified compositional criteria under adiabatic conditions to produce mononitrotoluene. The reaction mixture is then separated into an organic phase containing the mononitrotoluene and an acid phase.
The mononitrotoluene is then further nitrated with a nitrating acid satisfying specified compositional requirements under adiabatic conditions to produce dinitrotoluene. The reaction mixture is then separated into an organic phase containing dinitrotoluene and an acid phase. The acid phase recovered after each separation may be further treated and recycled.
DFTAII FD DFSCRIPTION OF THF INVFNTION
The present invention relates to a two-stage process for the continuous production of dinitrotoluene isomer mixtures by nitration of toluene. In the first stage of this process, toluene and nitrating acid are reacted under adiabatic conditions in a continuously operated reactor at a temperature of from 0 to about 140C, preferably from about 20 to about 140C. The nitrating acid is made up of (i) from about 80 to about 100%
215~9 Mo4239 - 5 -by weight (based on total weight of nitrating acid used in the first stage) of inorganic materials which include: from about 60 to about 90% by weight (based on total weight of inorganic materials in nitrating acid used in the first stage) of sulfuric acid, from about 1 to about 20% by weight 5 (based on total weight of inorganic materials in nitrating acid used in first stage) of nitric acid and at least 5% by weight (based on total weight of inorganic materials in nitrating acid used in first stage) of water; and (ii) from 0 to about 20% by weight (based on total weight of nitrating acid used in first stage) of organic materials which include from about 70 to 10 about 100% by weight (based on total weight of organic materials in nitrating acid used in first stage) of nitrotoluene isomers with the remainder being by-products of the nitration reaction. The molar ratio of nitric acid to toluene is at least 0.7:1 and at most 1.2:1. The reaction mixture is then separated into an acid phase and an organic phase 15 containing mononitrotoluene. At least 5% by weight of the water present in the acid phase is removed, preferably by distillation through flash evaporation. Nitric acid having a concentration of from 50 to 100% by weight is then added to the acid phase to replace the nitric acid consumed in the nitration reaction, if necessary, and is continuously 20 returned to the reaction vessel in which the toluene and nitrating acid are reacted. The organic phase containing mononitrotoluene (MNT) removed in the first stage is then reacted under adiabatic conditions with a nitrating acid made up of (i) from about 80 to about 100% by weight (based on total weight of nitrating acid used in second stage) of inorganic materials 25 which include from about 60 to about 90% by weight (based on total weight of inorganic materials in nitrating acid used in second stage) of sulfuric acid, from about 1 to about 20% by weight (based on total weight of inorganic materials in nitrating acid used in second stage) of nitric acid and at least 5% by weight (based on total weight of inorganic materials in 30 nitrating acid used in second stage) of water; and (ii) from about 0 to Mo4239 - 6 -about 20% by weight (based on total weight of nitrating acid used in second stage) of organic constituents which include from about 70 to about 100% by weight (based on total weight of organic materials in nitrating acid used in second stage) of nitrotoluene isomers with the remainder being by-products of the nitration reaction. This nitration reaction is carried out at temperatures of from about 20 to about 200C, preferably at temperatures of from about 40 to about 180C and more preferably at temperatures of from about 60 to about 170C. The MNT
and nitrating acid are used in quantities such that the molar ratio of nitric acid to mononitrotoluene is at least 0.7:1 and at most 1.2:1. The reaction mixture is then separated into an acid phase and an organic phase containing dinitrotoluene. At least 5% by weight of the water present in the acid phase from the second stage of the nitration process is removed, preferably by distillation through flash evaporation, optionally with application of heat. Nitric acid having a concentration of from 50 to 100% by weight is then added to the acid phase before that acid phase is continuously returned to the reaction vessel. Mononitrotoluene from the first stage of the process is added to the vapors present during the concentration of the second waste acid.
The quantity of MNT added is selected so that the vapor condensate runs off in liquid form and does not form any solid coating.
This may be achieved by adding the MNT in an amount such that the ratio by weight of MNT to DNT present in the organic phase of the vapor condensate is from about 2:1 to about 10:1. After phase separation, the organic constituents of the vapor condensate are returned to the first and/or second nitration stage.
The process of the present invention is preferably carried out with two nitrating acids of different concentration. A nitrating acid of low concentration is preferably used in the first stage so that selective nitration and energy-optimized concentration of the waste acid are 21~S!~i9 Mo4239 7 possible. A concentrated nitrating acid is used in the second stage in view of the greater nitrating demand.
Having thus described our invention, the following Examples are given as being illustrative thereof.
FxAMp! FS
Fxample 1 The reactor used in each stage of the nitration process included a mixing nozzle (internal diameter 0.2 mm) and two redispersing nozzles (internal diameter 0.3 mm). Dwell zones (internal diameter 2.0 mm) optimized for the particular reaction were present between the individual nozles.
100.5 g/h (1.090 moles/h) of toluene and 2,500 g/h (1.179 moles/h) of a nitrating acid composed of 72.4% by weight of sulfuric acid, 3.0% by weight of nitric acid and 24.6% by weight of water were continuously reacted under adiabatic conditions at 27C in a reactor such as that described above. The reaction mixture leaving the reactor was subjected to phase separation at approximately 50C. The waste acid was passed through a concentration stage and, after replenishment with 60% nitric acid, was returned to the first reaction stage. The organic phase separated off was reacted under adiabatic conditions at a temperature of about 50C in a second reactor with 2038.8 g/h (1.168 moles/h) of a nitrating acid made up of 79.9% by weight of sulfuric acid, 3.6% by weight of nitric acid and 16.5% by weight of water. Phase separation was then carried out. After separation, the waste acid was passed through a concentration stage. To avoid deposits in the condensation section, 15 g/h of MNT from the first nitration stage were introduced into the superheated vapors of the evaporator. After replenishment with 60% nitric acid, the concentrated waste acid was returned to the second nitration stage, as were the organic constituents of Mo4239 - 8 -the vapor condensate. The organic phase was washed in the usual way (with water and soda) and yielded 196.8 g/h of dinitrotoluene (99.0%).
Fxample ~
101.2 g/h (1.102 moles/h) of toluene and 2,500 ml/h (1.1903 5 moles/h) of a nitrating acid composed of 68.5% by weight of sulfuric acid, 3.0% by weight of nitric acid, and 28.5% by weight of water were -continuously reacted under adiabatic conditions at 85C in a reactor such as that described in Example 1. The reaction product leaving the reactor was separated into two phases at approximately 50C. The waste acid 10 was delivered to a concentration stage and, after replenishment with 60%
nitric acid, was returned to the first reaction stage. The organic phase containing mononitrotoluene was then reacted under adiabatic conditions with 2,072.9 g/h (1.183 moles/h) of a nitrating acid made up of 77.9% by weight of sulfuric acid, 3.6% by weight of nitric acid and 18.5% by weight 15 of water in a second reactor. The temperature at which this reaction began corresponded to the temperature of the recycled concentrated waste acid from the same stage after concentration and replenishment with fresh nitric acid. The dinitrotoluene was then isolated by phase separation and washed in the usual way with water and soda. The waste 20 acid obtained was concentrated. To avoid deposits in the condensation section, 8 g/h of MNT from the first nitration stage were introduced into the superheated vapors of the evaporator. After replenishment with 60%
nitric acid, the concentrated waste acid was returned to the second nitration stage, as were the organic constituents of the vapor condensate.
25 In continuous operation with closed circuits, the yield of dinitrotoluene was 197.6 g/h (98.7%).
21~5 9 Mo4239 9 Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of 5 the invention except as it may be limited by the claims.
BACKGROUND OF THF INVFI~ITION
This invention relates to a two-stage process for the production of dinitrotoluene from toluene and nitric acid in the presence of sulfuric acid.
Dinitrotoluene (DNT) is used to produce tolylene diisocyanate - (TDI). TDI is a starting material used in the production of polyurethane plastics. DNTis generally produced by reacting toluene with nitrating acid. This nitration reaction is carried out in two stages. Mononitro-toluene (MNT) is initially obtained by reacting toluene with a dilute nitrating acid. After removal of the spent sulfuric acid (hereinafter referred to as "waste acid"), the MNT is converted to DNT in a second process step. Both nitrating steps are carried out under isothermal conditions, i.e. with cooling to maintain a low temperature.
Two waste acids accumulate in the process and, after regeneration with nitric acid, may be returned to the process. The waste acid from the second stage can be directly recycled. The waste acid from the second stage may still have a concentration such that, after regeneration with nitric acid, it may be used without being concentrated beforehand. Accordingly, only the waste acid from the first stage has to be concentrated before being re-used. This is normally done by the Pauling process (Bedenbrenner, von Plessen, Vollmuller, Dechema-Monogr. 86 (1980), 197) although the vacuum process is also increasingly being used (\Ninnacker, Kuchler, Chem. Technol, Vol. 2, Anorg. Technol. I, 4th Edition, 1982, pages 70 to 72). In both of these acid concentration processes, energy must be introduced to remove the water of reaction.
During its recycling, the concentrated waste acid is replenished with highly concentrated nitric acid. Although nitric acids of low concentration, which are far less expensive, could be used in principle, Mo4239 - 2 -their use does involve the consumption of considerable additional energy because the waste acid has to be concentrated to a higher degree.
For the reasons mentioned above, efforts have long been made to improve the above-described nitration processes.
An improvement in terms of energy consumption may be achieved -by carrying out the mononitration of benzene under adiabatic conditions.
It was also found that it is possible to use more dilute nitric acids in such a process. The adiabatic process has been used industrially. See, for example, U.S. Patents 3,928,475; 4,021,498; 4,091,042 and 4,453,027;
and EP-A 436,443).
The adiabatic process was also applied to the production of aromatic dinitro compounds (EP-A 597,361). In this case, toluene is reacted with nitrating acid in a single stage to form DNT. By using nitrating acids with a special composition, it is possible to carry out the nitrating process under adiabatic conditions and to keep the heat of reaction in the system. There is no longer any need to cool the process, as in the conventional isothermal process, so that expensive cooling energy is saved. After separation of the phases, the hot waste acid is sprayed in vacuo and the heat of reaction of the process is used to concentrate the waste acid. Because the reaction is carried out under adiabatic conditions, i.e. at a high temperature, the process is able to accommodate the use of dilute nitric acid. Depending on the nitric acid used, there is little or no need for heating in the concentration step.
The disadvantage of this latter process is that both mononitration and dinitration are carried out with the same nitrating acid. Because nitration is intended to be quantitative, the reactivity of the nitrating acid has to be adapted to the dinitration step. Accordingly, the nitrating acid used in this known process is actually too concentrated for the mononitration step, so that mononitration takes place very quickly and, in some cases, with very little selectivity. Another disadvantage of this 21~5~9 Mo4239 - 3 known process is that a more concentrated waste acid than necessary accumulates in the mononitration step. Waste acids of relatively high concentration are much more expensive to concentrate in terms of energy because the heat of solution of water in sulfuric acid increases 5 with increasing sulfuric acid concentration.
Another disadvantage of this known process is that DNT dissolved in the waste acid also distills over in the concentration step. Under the conditions required for condensation of the water, the DNT crystallizes, covers the heat exchanger and thus impedes the transfer of heat.
A possible solution to this problem with respect to heat transfer is to use cyclic heat exchangers. Cyclic heat exchangers are operated alternately and any coatings formed are melted off during the phase in which the heat exchanger is not in operation. Coatings forrned on the heat exchange surfaces result in rapid reduction of cooling capacity.
15 Consequently, the heat exchangers need to be frequently alternated.
The removal of coatings formed from the inoperative condenser by melting requires additional energy.
Use of a mixing or injection condenser has been described as another possible solution to the problem of condensing solids-forrning 20 vapors (R.A. Vauck, H.A. Muller, Grundoperationen chemischer Verfahrenstechnik, 5th Edition, VEB Leipzig (1962), page 447). In the mixing or injection condenser, the vapors are introduced into a jet spray of cold water. DNT is deposited in the form of a fine particulate solid when such an injection condenser is used. In view of the large quantities 25 of water required in these processes, the water is circulated and cooled in the return branch of the circuit. However, pipes and nozzles are subject to blockage by low melting, inorganic components which tend to become tacky.
One elegant solution to this problem is the isotherrnal two-stage 30 nitration process. In this process, MNT from the first nitration stage is 21 S 5 3 ~ 9 Mo-4239 4 injected into the vapors of the second concentration stage. The MNT
introduced reduces the melting point of the DNT isomer mixture and the condensed mixture remains liquid (DE-A 3,409,719).
SUMMARY OF THF INVFNTION
It is an object of the present invention to provide a process for the production of dinitrotoluene in which dilute nitric acid may be used.
- It is also an object of the present invention to provide a process for the production of dinitrotoluene which utilizes the heat of reaction.
It is a further object of the present invention to provide a process for the production of dinitrotoluene in which problems due to condensation of the vapors in the waste acid concentration step are avoided.
These and other objects which will be apparent to those skilled in the art are accomplished by nitrating toluene with a nitrating acid satisfying specified compositional criteria under adiabatic conditions to produce mononitrotoluene. The reaction mixture is then separated into an organic phase containing the mononitrotoluene and an acid phase.
The mononitrotoluene is then further nitrated with a nitrating acid satisfying specified compositional requirements under adiabatic conditions to produce dinitrotoluene. The reaction mixture is then separated into an organic phase containing dinitrotoluene and an acid phase. The acid phase recovered after each separation may be further treated and recycled.
DFTAII FD DFSCRIPTION OF THF INVFNTION
The present invention relates to a two-stage process for the continuous production of dinitrotoluene isomer mixtures by nitration of toluene. In the first stage of this process, toluene and nitrating acid are reacted under adiabatic conditions in a continuously operated reactor at a temperature of from 0 to about 140C, preferably from about 20 to about 140C. The nitrating acid is made up of (i) from about 80 to about 100%
215~9 Mo4239 - 5 -by weight (based on total weight of nitrating acid used in the first stage) of inorganic materials which include: from about 60 to about 90% by weight (based on total weight of inorganic materials in nitrating acid used in the first stage) of sulfuric acid, from about 1 to about 20% by weight 5 (based on total weight of inorganic materials in nitrating acid used in first stage) of nitric acid and at least 5% by weight (based on total weight of inorganic materials in nitrating acid used in first stage) of water; and (ii) from 0 to about 20% by weight (based on total weight of nitrating acid used in first stage) of organic materials which include from about 70 to 10 about 100% by weight (based on total weight of organic materials in nitrating acid used in first stage) of nitrotoluene isomers with the remainder being by-products of the nitration reaction. The molar ratio of nitric acid to toluene is at least 0.7:1 and at most 1.2:1. The reaction mixture is then separated into an acid phase and an organic phase 15 containing mononitrotoluene. At least 5% by weight of the water present in the acid phase is removed, preferably by distillation through flash evaporation. Nitric acid having a concentration of from 50 to 100% by weight is then added to the acid phase to replace the nitric acid consumed in the nitration reaction, if necessary, and is continuously 20 returned to the reaction vessel in which the toluene and nitrating acid are reacted. The organic phase containing mononitrotoluene (MNT) removed in the first stage is then reacted under adiabatic conditions with a nitrating acid made up of (i) from about 80 to about 100% by weight (based on total weight of nitrating acid used in second stage) of inorganic materials 25 which include from about 60 to about 90% by weight (based on total weight of inorganic materials in nitrating acid used in second stage) of sulfuric acid, from about 1 to about 20% by weight (based on total weight of inorganic materials in nitrating acid used in second stage) of nitric acid and at least 5% by weight (based on total weight of inorganic materials in 30 nitrating acid used in second stage) of water; and (ii) from about 0 to Mo4239 - 6 -about 20% by weight (based on total weight of nitrating acid used in second stage) of organic constituents which include from about 70 to about 100% by weight (based on total weight of organic materials in nitrating acid used in second stage) of nitrotoluene isomers with the remainder being by-products of the nitration reaction. This nitration reaction is carried out at temperatures of from about 20 to about 200C, preferably at temperatures of from about 40 to about 180C and more preferably at temperatures of from about 60 to about 170C. The MNT
and nitrating acid are used in quantities such that the molar ratio of nitric acid to mononitrotoluene is at least 0.7:1 and at most 1.2:1. The reaction mixture is then separated into an acid phase and an organic phase containing dinitrotoluene. At least 5% by weight of the water present in the acid phase from the second stage of the nitration process is removed, preferably by distillation through flash evaporation, optionally with application of heat. Nitric acid having a concentration of from 50 to 100% by weight is then added to the acid phase before that acid phase is continuously returned to the reaction vessel. Mononitrotoluene from the first stage of the process is added to the vapors present during the concentration of the second waste acid.
The quantity of MNT added is selected so that the vapor condensate runs off in liquid form and does not form any solid coating.
This may be achieved by adding the MNT in an amount such that the ratio by weight of MNT to DNT present in the organic phase of the vapor condensate is from about 2:1 to about 10:1. After phase separation, the organic constituents of the vapor condensate are returned to the first and/or second nitration stage.
The process of the present invention is preferably carried out with two nitrating acids of different concentration. A nitrating acid of low concentration is preferably used in the first stage so that selective nitration and energy-optimized concentration of the waste acid are 21~S!~i9 Mo4239 7 possible. A concentrated nitrating acid is used in the second stage in view of the greater nitrating demand.
Having thus described our invention, the following Examples are given as being illustrative thereof.
FxAMp! FS
Fxample 1 The reactor used in each stage of the nitration process included a mixing nozzle (internal diameter 0.2 mm) and two redispersing nozzles (internal diameter 0.3 mm). Dwell zones (internal diameter 2.0 mm) optimized for the particular reaction were present between the individual nozles.
100.5 g/h (1.090 moles/h) of toluene and 2,500 g/h (1.179 moles/h) of a nitrating acid composed of 72.4% by weight of sulfuric acid, 3.0% by weight of nitric acid and 24.6% by weight of water were continuously reacted under adiabatic conditions at 27C in a reactor such as that described above. The reaction mixture leaving the reactor was subjected to phase separation at approximately 50C. The waste acid was passed through a concentration stage and, after replenishment with 60% nitric acid, was returned to the first reaction stage. The organic phase separated off was reacted under adiabatic conditions at a temperature of about 50C in a second reactor with 2038.8 g/h (1.168 moles/h) of a nitrating acid made up of 79.9% by weight of sulfuric acid, 3.6% by weight of nitric acid and 16.5% by weight of water. Phase separation was then carried out. After separation, the waste acid was passed through a concentration stage. To avoid deposits in the condensation section, 15 g/h of MNT from the first nitration stage were introduced into the superheated vapors of the evaporator. After replenishment with 60% nitric acid, the concentrated waste acid was returned to the second nitration stage, as were the organic constituents of Mo4239 - 8 -the vapor condensate. The organic phase was washed in the usual way (with water and soda) and yielded 196.8 g/h of dinitrotoluene (99.0%).
Fxample ~
101.2 g/h (1.102 moles/h) of toluene and 2,500 ml/h (1.1903 5 moles/h) of a nitrating acid composed of 68.5% by weight of sulfuric acid, 3.0% by weight of nitric acid, and 28.5% by weight of water were -continuously reacted under adiabatic conditions at 85C in a reactor such as that described in Example 1. The reaction product leaving the reactor was separated into two phases at approximately 50C. The waste acid 10 was delivered to a concentration stage and, after replenishment with 60%
nitric acid, was returned to the first reaction stage. The organic phase containing mononitrotoluene was then reacted under adiabatic conditions with 2,072.9 g/h (1.183 moles/h) of a nitrating acid made up of 77.9% by weight of sulfuric acid, 3.6% by weight of nitric acid and 18.5% by weight 15 of water in a second reactor. The temperature at which this reaction began corresponded to the temperature of the recycled concentrated waste acid from the same stage after concentration and replenishment with fresh nitric acid. The dinitrotoluene was then isolated by phase separation and washed in the usual way with water and soda. The waste 20 acid obtained was concentrated. To avoid deposits in the condensation section, 8 g/h of MNT from the first nitration stage were introduced into the superheated vapors of the evaporator. After replenishment with 60%
nitric acid, the concentrated waste acid was returned to the second nitration stage, as were the organic constituents of the vapor condensate.
25 In continuous operation with closed circuits, the yield of dinitrotoluene was 197.6 g/h (98.7%).
21~5 9 Mo4239 9 Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of 5 the invention except as it may be limited by the claims.
Claims (10)
1. A continuous process for the production of dinitrotoluene isomer mixtures comprising (A) reacting (1 ) toluene with (2) nitrating acid which is made up of (i) from about 80 to about 100% by weight of inorganic materials which include:
(a) from about 60 to about 90% by weight of sulfuric acid, (b) from about 1 to about 20% by weight of nitric acid and (c) at least 5% by weight of water and (ii) from 0 to about 20% by weight of organic materials of which at least 70% by weight are isomers of nitrotoluene in amounts such that the molar ratio of nitric acid to toluene is between 0.7:1 and 1.2:1 under adiabatic conditions in a continuously operated reactor at a temperature of from about 0 to about 140°C, (B) separating the reaction mixture of (A) into an acid phase and an organic phase containing mononitrotoluene, (C) removing at least 5% by weight of water from the acid phase separated in (B), (D) adding nitric acid to the acid phase from (C), (E) recycling the acid phase from (D), (F) reacting the mononitrotoluene in the organic phase from (B) with a nitrating acid which is made up of (i) from about 80 to about 100% by weight of inorganic materials which include:
(a) from about 60 to about 90% by weight of sulfuric acid, (b) from about 1 to about 20% by weight of nitric acid and (c) at least 5% by weight of water and (ii) from 0 to about 20% by weight of organic materials of which 70% by weight or more are isomers of nitrotoluene in amounts such that the molar ratio of nitric acid to mononitrotoluene is between 0.7:1 and 1.2:1 under adiabatic conditions at a temperature of from about 40 to about 180°C and (G) separating the reaction mixture of (F) into an acid phase and an organic phase containing dinitrotoluene, (H) removing at least 5% by weight of water from the acid phase from (G), (I) adding mononitrotoluene to the vapors generated in (H), (J) adding nitric acid to the acid phase from (H), (K) recycling the acid phase from (J) to the reaction vessel in which (F) is carried out, and (L) recovering dinitrotoluene from the organic phase of (G).
(a) from about 60 to about 90% by weight of sulfuric acid, (b) from about 1 to about 20% by weight of nitric acid and (c) at least 5% by weight of water and (ii) from 0 to about 20% by weight of organic materials of which at least 70% by weight are isomers of nitrotoluene in amounts such that the molar ratio of nitric acid to toluene is between 0.7:1 and 1.2:1 under adiabatic conditions in a continuously operated reactor at a temperature of from about 0 to about 140°C, (B) separating the reaction mixture of (A) into an acid phase and an organic phase containing mononitrotoluene, (C) removing at least 5% by weight of water from the acid phase separated in (B), (D) adding nitric acid to the acid phase from (C), (E) recycling the acid phase from (D), (F) reacting the mononitrotoluene in the organic phase from (B) with a nitrating acid which is made up of (i) from about 80 to about 100% by weight of inorganic materials which include:
(a) from about 60 to about 90% by weight of sulfuric acid, (b) from about 1 to about 20% by weight of nitric acid and (c) at least 5% by weight of water and (ii) from 0 to about 20% by weight of organic materials of which 70% by weight or more are isomers of nitrotoluene in amounts such that the molar ratio of nitric acid to mononitrotoluene is between 0.7:1 and 1.2:1 under adiabatic conditions at a temperature of from about 40 to about 180°C and (G) separating the reaction mixture of (F) into an acid phase and an organic phase containing dinitrotoluene, (H) removing at least 5% by weight of water from the acid phase from (G), (I) adding mononitrotoluene to the vapors generated in (H), (J) adding nitric acid to the acid phase from (H), (K) recycling the acid phase from (J) to the reaction vessel in which (F) is carried out, and (L) recovering dinitrotoluene from the organic phase of (G).
2. The process of Claim 1 in which nitric acid having a concentration of from 50 to 100% by weight is added in (D).
3. The process of Claim 2 in which the water is removed from the acid phase by flash evaporation.
4. The process of Claim 2 in which nitric acid having a concentration of from 50 to 100% by weight is added in (J).
5. The process of Claim 4 in which the water is removed from the acid phase by flash evaporation.
6. The process of Claim 1 in which nitric acid having a concentration of from 50 to 100% by weight is added in (J).
7. The process of Claim 6 in which the water is removed from the acid phase by flash evaporation.
8. The process of Claim 1 in which (A) is carried out at a temperature of from about 20 to about 140°C.
9. The process of Claim 1 in which (F) is carried out at a temperature of from about 40 to about 180°C.
10. The process of Claim 1 in which (F) is carried out at a temperature of from about 60 to about 170°C.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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DEP4428459.4 | 1994-08-11 | ||
DE4428459A DE4428459A1 (en) | 1994-08-11 | 1994-08-11 | Process for the production of dinitrotoluene |
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CA2155559A1 true CA2155559A1 (en) | 1996-02-12 |
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CA002155559A Abandoned CA2155559A1 (en) | 1994-08-11 | 1995-08-07 | Process for the production of dinitrotoluene |
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US (1) | US5679873A (en) |
EP (1) | EP0696570B1 (en) |
JP (1) | JP3631812B2 (en) |
KR (1) | KR100357406B1 (en) |
CN (1) | CN1075051C (en) |
BR (1) | BR9503610A (en) |
CA (1) | CA2155559A1 (en) |
DE (2) | DE4428459A1 (en) |
ES (1) | ES2111994T3 (en) |
TW (1) | TW499408B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN103140464A (en) * | 2010-07-28 | 2013-06-05 | 拜耳知识产权有限责任公司 | Method for producing nitrobenzene by adiabatic nitriding |
Families Citing this family (11)
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DE19745119A1 (en) | 1997-10-13 | 1999-04-15 | Bayer Ag | Process for the production of dinitrotoluene in an adiabatic procedure |
DE10304615A1 (en) | 2003-02-05 | 2004-08-19 | Bayer Ag | Process for monitoring and managing nitriding processes with the help of online spectrometers |
DE10307140A1 (en) * | 2003-02-20 | 2004-09-09 | Bayer Ag | Two-stage nitration of toluene to produce dinitrotoluene has an adiabatic and then an isothermal stage so as to give heat savings and improve safety |
DE102004005913A1 (en) | 2004-02-05 | 2005-08-25 | Basf Ag | Process for the preparation of dinitrotoluene |
DE102006033722A1 (en) * | 2006-07-21 | 2008-01-24 | Bayer Materialscience Ag | Process for the preparation of dinitrotoluene |
DE102007059513A1 (en) * | 2007-12-11 | 2009-06-18 | Bayer Materialscience Ag | Process for the preparation of nitrobenzene by adiabatic nitration |
CN103304421A (en) * | 2013-06-26 | 2013-09-18 | 南京理工大学 | Method for preparing dinitrotoluene by nitrifying ortho-nitrotoluene with fuming sulfuric acid-nitric acid system |
CN104016867B (en) * | 2014-06-19 | 2016-07-06 | 山东师范大学 | The synthetic method of 1-nitro-3,4:9,10-tetrabasic ester and 1,6 (7)-dinitro-3,4:9,10-tetrabasic esters |
CN104387388B (en) * | 2014-12-15 | 2016-09-07 | 山东师范大学 | A kind of novel method for synthesizing of position, gulf azacyclo-3,4:9,10-tetracarboxylic acid diimide |
CN104513174B (en) * | 2014-12-24 | 2016-01-06 | 浙江荣耀生物科技有限公司 | The utilization process of the spent acid in a kind of ball dysentery spirit production process and device |
CN110172023A (en) * | 2019-04-04 | 2019-08-27 | 清华大学 | A kind of method of adiabatic nitration preparation mononitrotoluene |
Family Cites Families (10)
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US3928475A (en) * | 1974-08-09 | 1975-12-23 | Du Pont | Azeotropic nitration of benzene |
US4021498A (en) * | 1975-12-09 | 1977-05-03 | American Cyanamid Company | Adiabatic process for nitration of nitratable aromatic compounds |
US4091042A (en) * | 1977-08-19 | 1978-05-23 | American Cyanamid Company | Continuous adiabatic process for the mononitration of benzene |
US4453027A (en) * | 1982-12-10 | 1984-06-05 | Monsanto Company | Adiabatic process for the nitration of halobenzenes |
US4496782A (en) * | 1983-07-08 | 1985-01-29 | Air Products And Chemicals, Inc. | Nitric acid recovery by the adiabatic nitration of nitroaromatics with fortified spent acid |
DE3409719A1 (en) * | 1984-03-16 | 1985-09-19 | Bayer Ag, 5090 Leverkusen | METHOD FOR PRODUCING DINITROTOLUOL |
US4650912A (en) * | 1985-03-26 | 1987-03-17 | Air Products And Chemicals, Inc. | Recovery of nitric acid from nitration spent acid by toluene extraction |
DE69026590T2 (en) * | 1990-01-04 | 1996-10-31 | Nrm Int Tech | Nitriding process |
DE4309140C2 (en) * | 1993-03-22 | 2001-09-20 | Bayer Ag | Process for the production of dinitrotoluene |
TW236610B (en) * | 1992-11-13 | 1994-12-21 | Bayer Ag | Preparation of dinitrotoluene |
-
1994
- 1994-08-11 DE DE4428459A patent/DE4428459A1/en not_active Withdrawn
-
1995
- 1995-07-31 EP EP95111993A patent/EP0696570B1/en not_active Expired - Lifetime
- 1995-07-31 ES ES95111993T patent/ES2111994T3/en not_active Expired - Lifetime
- 1995-07-31 DE DE59501267T patent/DE59501267D1/en not_active Expired - Lifetime
- 1995-08-03 US US08/510,992 patent/US5679873A/en not_active Expired - Lifetime
- 1995-08-07 CA CA002155559A patent/CA2155559A1/en not_active Abandoned
- 1995-08-09 JP JP22278995A patent/JP3631812B2/en not_active Expired - Fee Related
- 1995-08-10 KR KR1019950024650A patent/KR100357406B1/en not_active IP Right Cessation
- 1995-08-10 BR BR9503610A patent/BR9503610A/en active Search and Examination
- 1995-08-11 CN CN95109292A patent/CN1075051C/en not_active Expired - Fee Related
- 1995-08-11 TW TW084108356A patent/TW499408B/en not_active IP Right Cessation
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103140464A (en) * | 2010-07-28 | 2013-06-05 | 拜耳知识产权有限责任公司 | Method for producing nitrobenzene by adiabatic nitriding |
CN103140464B (en) * | 2010-07-28 | 2014-12-03 | 拜耳知识产权有限责任公司 | Method for producing nitrobenzene by adiabatic nitriding |
Also Published As
Publication number | Publication date |
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EP0696570A1 (en) | 1996-02-14 |
KR100357406B1 (en) | 2003-01-15 |
CN1121066A (en) | 1996-04-24 |
ES2111994T3 (en) | 1998-03-16 |
DE4428459A1 (en) | 1996-02-15 |
EP0696570B1 (en) | 1998-01-14 |
TW499408B (en) | 2002-08-21 |
JPH0859562A (en) | 1996-03-05 |
US5679873A (en) | 1997-10-21 |
KR960007528A (en) | 1996-03-22 |
JP3631812B2 (en) | 2005-03-23 |
CN1075051C (en) | 2001-11-21 |
DE59501267D1 (en) | 1998-02-19 |
BR9503610A (en) | 1996-04-30 |
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